Hello,
Yes yes, another Power vs Thrust question
I understand the basics, I know the details, but I don't really understand the details.
I searched through the forum, read all the power vs thrust threads, but still I'm struggling with it.
Here is what I know (please correct me if I'm wrong):
- Power = thrust x time
- Piston engine: engine produces power, fuel flow depends on power produced, power goes to propeller, propeller produces thrust.
- Jet engine: engine produces thrust directly, so fuel flow depends on the thrust produced.
Those 3 arguments are perfectly clear.
- All engines: best angle of climb speed (Vx) happens when the excess thrust is the greatest
- All engines: best rate of climb speed (Vy) happens when the excess power is the greatest
It's with those 2 I have an issue.
For Vx I'd say okay, excess thrust. Why? A jet engine produces thrust, so here we're already talking about thrust. And with a piston engine: it's not because there's a lot of excess power that there's the same amount of excess thrust (a propeller's effiency depends on a lot of other factors).
But what about Vy? Why can't we say that for the best Vy we need the greatest excess thrust? Okay, power = thrust x time, and with Vy time is an important factor. But: thrust = power/time. Here we also consider the time.
Hopefully I'm clear about what it is that I don't fully understand.
Thanks in advance.